'''with open("bill.txt","r+",encoding = "utf-8")as f,open("bill.txt.bak","w",encoding = "utf-8") as f_bak:
    #备份
    res = f.read()
    f_bak.write(res)

    #内容删除
    s = ""
for line in res.split('\n'):
    #如果找不到返回-1
    if line.find('测试') == -1:
        s += line + '\n'


#回转指针
f.seek(0)
#清空内容
f.truncate()
#写入内容
f.write(s)
'''


# 读取bil.txt中的内容
f = open('./files/bil.txt','r',encoding='utf-8')
 res = f.read()
 f.close()
# # 写入bil.txt.bak中
 f_bak = open('./files/bil.txt.bak','w',encoding='utf-8')
 f_bak.write(res)
 f_bak.flush()

with open('./files/bil.txt','r+',encoding='utf-8') as f,open('./files/bil.txt.bak','w',encoding='utf-8') as f_bak:
    # 备份
    res = f.read()
    f_bak.write(res)

    # 内容删除
    s = ""   
    for line in res.split('\n'):
        # 如果找不到返回-1
        if line.find('测试') == -1:
            s += line + '\n'


    # 回转指针
    f.seek(0)
    # 清空内容
    f.truncate()


    
    # 写入新内容
    f.write(s)

